Strictly speaking, Aikido-ka would never find themselves in a competitive match: competitions means there will be a winner and a loser, and that concept is anathama to Aikido.
Strictly speaking, there are no aggressive strategies in Aikido, therefore, they would never attack.
But Aikido-ka are humans, and humans have free will. Attack a human being who knows Aikido, and you might end up with a broken shoulder, or you might not: the outcome is not because of anything to do with Aikido, it has everything to do with the choices that Aikido-ka made. They are free to compete, but the techniques are not designed for competitive edge. And that was the basis for my previous answer: since there is no "reason" to attack (getting points or a KO), and since there are no aggressive strategies in Aikido, the Aikido-ka can only logically wait for the strike to come.
In training, though, we do practice realistic strikes. Beginners don't: they are more concerned with the principles of attack and defense. As they become more senior, they are free to resist and become more free-form in their performance. People quit Aikido before they get to this point, because usually, they are frustrated with the progression to "realism" and "resistance". Honestly, if they had given it more time and patience, they'd have understood this.
When you have someone's wrist in your control, it is but a quarter-inch in any direction that can make the person think twice about their actions. If they are hell bent on continuing with their attack, or if the Aikido-ka thinks that letting them go would be disasterous for the Aikido-ka, then a step outside the strategies of Aikido is necessary: the wrist must be broken. Will the heavens part the clouds and an admonishing finger be wagged at the Aikido-ka for doing this? Will the Aikido-ka be banned from further practice, or be stripped of rank? No, of course not.
Pure Aikido is defense only. But, like yin and yang, it requires to understand committed strikes, and a variety of offensive movements, in order for it to be practiced. And humans are rarely pure at anything. So oftentimes, the question of Aikido's effectiveness (notwithstanding the issue of the matter that the stylist, and not the style, is the one who's effective) is based on several misunderstandings: that Aikido has no offense (that is true, but that doesn't necessarily apply to the stylist, who is free to add in whatever offense their ethics requires); or that Aikido is purely defensive.